Piston



- "Patented 7 July 14, 1936 1 UNITED STATES- PATENT OFFICE PISTON Ray E. Day, Detroit, Mich. Application October 9',- 1933, Serial No. 692,752

"To Claim. (o cos-11) part of my co-pending application, Serial No.

623,064, filed July 18, 1932.

I have found that there are two principal fac- 15 tors which control the successful manufacture and sale of a low price commercially practical piston. First, the design of the piston must be simplified in order to facilitate casting of the pistons and to reduce the cost of manufacture. Second, the piston must be so constructed in simplified manner as to take care of expansion and contraction'under operating conditions, maintain a nearly imiform operating fit in the cylinder, and efiectually guide the piston in order to preventrocking or tilting of the piston and piston slap. I

An object of the present invention is to provide a piston of simplified'construction which can be produced cheaply and which at the same time is constructed in improved manner so as to have the desired high degree of efliciency in operation without resorting to structural expedients, many of questionable value, as heretofore.

Other. objects ofthis invention will appear in the following description and appended claims,

reference being had to the accompanying drawing forming a part of this specification wherein parts in the several views. :40 In said drawing:

likereference characters designate corresponding Fig. l is an elevational view of a piston made in accordance with my invention.

Fig. 2 is an elevational view of the low thrust side or face of the piston of Fig. 1.

Fig. 3 is a vertical section taken substantially tionis capable of other embodiments and of being practiced or. carried out in various ways. Also it is to be understood that the phraseology or terminology employedherein is for the purpose of 60 description and not of limitation, and it is not :the piston pin openings is, each of said relieved intended to limit the invention claimed herein beyond the requirements of the prior art.-

Referring now particularly to the drawing, my

improved piston is shown as'a whole at II, and

7 comprises a head portion ll provided with Pist n 5 ring grooves l2, the lowermost groove having a series of oil escape holes or openings it formed therein. The head H is internally reenforced by a pair of'ribs ll. The piston skirt isshown at 15 and has a low thrust face or side L and a high 10 thrust face or side H. The low thrust side of the skirt is provided with an upright slot l6 which extends from the bottom of the skirt and intercepts a horizontal slot I1. The slot ll serves to separate the head and skirt on the low thrust 15 side. The skirt carries a pair of piston pin bosses or bearings l8 having the usual piston pin openings l9. Theskirt is reenforced internally-by ribs 9.

' a Referring to Fig. 5, it will be seen that the high thrust face or side Hof the piston skirt is sepa- 20 rated frointhe head at two points by a pair of spaced horizontal slots 2|). At points between the endsof the slots l1 and 20, the head and skirt piston, midway between the bosses (see Figs. 2 and 4) Thus it will be seen that there are three points of connection between the head and the skirt. 30 The upright slot l6 and the horizontal slots l1 and 20 may be formed by milling cutters, in which case the complete piston is formed in the mold and the several parts later separated by the application of the cutter to form tlie aforesaid slots. 35

However, the slots may be preformed during the molding operation.

The skirt is provided on opposite sides with relieved areas 122, located at points surrounding areas comprising portions a and b. The portion it toward the low thrustside of the piston is of greater area than the portion 11 toward the high thrust side or face, thus'providing a piston which 45 has a greater efiective bearing surface on the high thrust side than 'on the low thrust side. If

.desired, the piston wall may be ma'de slightly thicker at the center of the high thrust side, as

shown at 23, to reenforce that side of the piston.

It is.particularly advantageous and desirable to prevent the piston from rocking within the cylinder dining operation, To accomplish this,

I have'\provided the skirtswith relatively .narrow bearing portions or strips 24 and 25 which are located at the upper edges" of the relieved areas 22 and extend inwardly from the sideedges of said areas toward the piston pin openings l9. It will be noted that the bearing portions 25 are slightly longer than the bearing portions 24, thus providing some additional bearing sinface on the the piston pin bosses. I'hehead and skirt being connected together, thisexpansion of the'head has a tendency to expand the skirt in the same manner. By reason of the connection 2| between the head and the high thrust face H, the expansion of the head in the direction of the piston' pin bosses it! exerts an outward pull (in the direction of the bosses) on the middle of the high' thrust face and causes a slight flattening of the face below the slots 20, thus preventing scufling at the sides of the high thrust face. This not only preserves the piston but also prevents scoring of the cylinder wall. i

In practice, the piston is placed in the engine cylinder in such a position that the reaction due to the compression will be directed against the relatively resilient or split side of the piston, while the reaction due to the explosion, which is much greater, will be directed against the side where the head and skirt'are integral or con tinuous.

It will be seen that the widest portion of each unbalanced relieved area is on the compression or split side of the piston, whereas the smaller portion of the relieved area is on the explosion or high thrust side., Since the high thrust side of the piston is subjected to greater pressure than thelow thrust side I have found it preferable to have a larger bearing surface on the high thrust side. By thus reducing the area of the bearing surface on the 'lowthrust or'compression side of the piston it ,will be seen that the vflexibility of that side of the piston is increased to eliminate any possibility of binding of the piston.

With previous types of pistons having resilient skirt portions provided with open relieved areas, it has been found that there was a tendency of the piston to rock or tilt in the cylinder, causing the objectionable slapping of the piston; This is obviated in the present construction by the bearing strips or portions 24 and 25 located above the unbalanced relief areas. These bearing strips together with the bearing portions of the skirt below'the relief areas 22, serve to guide the piston in the cylinder and also to prevent it from rocking. These bearing portionsthus assist in guiding the piston at-points between the skirt and the lower ring groove, but they are interits low thrust side and separated at said side from the head by a circumferential, slit, said piston having an unbalanced relieved area around each piston pin opening providing a wider portion on the split side than on the opposite side,

' and unbalanced bearing strips between. the lower ring groove and each unbalanced relieved area spaced at opposite sides of the vertical center ofthe piston pin opening and providing a. longer bearing strip above the wider portion' of the unbalancedrelieved area than above the narr'owe portion.

' and piston pin bosses are united.

2. A piston comprising a head, a skirt, and piston pin bosses, said skirt being vertically split at its low thrust side and separated at said side from the head by a circumferential slit, said piston having an unbalanced relieved area around each 5 -ing strip above the narrower portion of the un-' balanced relieved area than above the wider portion, said piston having unconnected circumferential slits separating said shorter bearing 15 strips from the piston head.

3. A pistoncomprisi g ahead, a skirt, and piston pin bosses, said skirt being vertically split at its low thrust side and separated at said side from the head by a circumferential slit, said pis 2 ton having an unbalanced relieved area around each piston pin opening providing a wider portion on the split side than on the opposite side, and unbalanced bearing strips between the lower ring groove and each unbalanced relieved area spaced 25' at opposite sides of the vertical center of the piston pin .opening and providing a shorter bearing strip above the narrower portion of the un-;- balanced relieved area than above the wider portion, said piston having unconnected circumfere 3oential slits separating said shorter bearing strips from the piston head, said slits terminating short 'of said first named circumferential slit at the integral relieved area through which the head 4. A piston comprising a head, a skirt, and piston pin openings, said skirt having an unbah anced relieved area around each piston pin opening providing-a wider portion on one side of the opening than on the other side, and unbalanced bearing strips between the lower ring groove and each unbalanced relieved area spaced at opposite sides of the vertical center of the piston pin opening and providing a longer bearing strip above the wider portion of the unbalanced. 1'6-7. lieved area than 'a ve the narrower portion.

5; Ina piston, the combination of a head having ring grooves therein, a skirt and piston pin bosses, said piston having an unbalanced relieved area around apiston pin opening providing a wider portion on one sideof the opening than, on the other side, and unbalanced bearing strips extending into the unbalanced relieved area adjacent the lower ring/ groove, the opposed ends of said bearing strips being spaced apart in the area immediately above the piston pin opening 6. In a piston, the combination of a head having ring grooves therein, a skirt and piston pin bosses, said piston having an unbalanced relievedarea around a piston pinopening providing a wider portion on one side of the opening than on the other'side, unbalanced bearing strips projecting into the unbalanced relieved area in the vicinity of the lower ring groove, the free ends of said bearingstripsbeing spaced apart in the area immediately above the piston pin opening and the longer "of said bearing strips being immediately above the wider portion of said relieved area.

. RAY E. DAY. 

